The purpose of this study is to develop an automated method for identifying malignant epithelial cells in urinary sediment specimens by using multiparameter photometric measurements that reflect the physical and biochemical characteristics of bladder cancer cells and permit them to be recognized by manual microscopy. An ultra-rapid flow-through cytofluorimeter (Cytofluorograf-Bio/Physics Systems, Inc.) is being used to quantitate the metachromatic fluorescence of acridine orange stained cells, and their light scatter, at rates of 1000 cells/second. Several different types of cells and other particulates can be distinguished in this way, and continuing improvement in discrimination is expected with modifications of specimen preparation and the parameters measured.